(1) Field of the Invention
The present invention relates generally to anodizing systems including a coating thickness monitor and, more particularly, to a system for regulating an anodized coating thickness on a substrate as it is being formed as well as measuring the coating thickness subsequent to its formation.
(2) Description of the Prior Art
The coating of metallic substrates such as aluminum and zinc using anodizing is known. Anodizing is done for practical and aesthetic reasons. From a practical perspective, the creation of a coating on the surface of a metallic substrate contributes to an anodized product""s wear resistance, corrosion resistance, and oxidation resistance. From an aesthetic perspective, the creation of a coating including a dye for coloration on the surface of a metallic substrate contributes to an anodized product""s consumer appeal. In both industrial and aesthetic applications, it is desirable to control the thickness of the anodized coating as well as the consistency over a given surface area.
Commonly, coating thickness is determined by destructive methods. For example, in a batch anodizing system, control coupons made of the same material as a product to be anodized are included in the anodizing bath. At intermediate times during the anodizing process a control coupon is removed from the bath and destroyed in a manner that permits determining the coating thickness.
One destructive method includes mounting a control coupon in a Bakelite cross-section, polishing the mounted coupon to a mirror finish and examining the polished cross-section using an optical microscope to determine the coating thickness. A second destructive method includes cutting or breaking a control coupon to expose a cross-section and examining the cross-section using scanning electron microscopy to determine the coating thickness. These destructive methods are cumbersome in production.
Both destructive methods delay production because of the time taken to remove and prepare control coupons for determining coating thickness. During the delay, the bath is idle. An alternative is to remove the product from the anodizing bath while determining coating thickness and replace it with a second product and corresponding control coupons. In this case, storage area for the product removed from the bath during a coating thickness determination would be required at the production site.
Although using an anodizing bath alternatively with multiple products provides a solution to production delay, coating flaws can be introduced by bath chemistry changes and surface contagion during storage. That is, the different bath chemistry when the product is reintroduced after the coating thickness determination for further anodizing may create a distinct mismatched interface with the original coating
During storage, the original coating on the product may also be damaged during removal from and replacement into the anodizing bath. Particulate matter such as dust also may attach to the surface to introduce further interfacial flaws between the original coating and the further coating.
The above destructive methods have another serious flaw, namely, that the determined coating thickness is that of a control coupon and not of the product. Thus, the coating thickness of the product is only an estimate and the coating thickness consistency over the entire surface of the product is unknown.
Thus, there remains a need for a new and improved anodizing system that includes a coating thickness monitor that nondestructively determines the coating thickness on a product, while at the same time, has the ability to control the anodizing system. There also remains a need for a coating thickness monitor that nondestructively determines the coating thickness on an anodized product.
The present invention is directed to an anodizing system for forming an anodized coating on at least a portion of a substrate thereby creating an anodized substrate. The anodizing system includes a bath, a coating thickness monitor, at least one probe, and at least one controller. The substrate is placed into the bath to facilitate the formation of the anodized coating on at least a portion of the substrate, thereby creating the anodized substrate. The coating thickness monitor measures the thickness of at least a portion of the anodized coating formed on the substrate in the bath. The coating thickness monitor includes at least one radiation source directed at at least a portion of the anodized substrate; at least one probe for capturing at least a portion of the radiation reflected and refracted by the anodized coating on the anodized substrate, the captured radiation being at least a portion of the radiation directed the anodized substrate from the radiation source; at least one detector in communication with the at least one probe, the at least one detector capable of processing the captured radiation to allow a determination of at least the thickness of the anodized coating on the substrate; and at least one guide system capable of transmitting the captured radiation from the at least one probe to the at least one detector. The at least one controller is in communication with the coating thickness monitor and the bath.
In one embodiment, the at least one controller regulates a relative movement of the probe and the anodized substrate. In another embodiment, the at least one controller regulates at least one process parameter of the bath. Preferably, the regulate process parameter includes at least one of bath chemistry, bath temperature, anodizing voltage, anodizing current and anodizing time. In another embodiment, the at least one controller regulates a process endpoint.
The guide system for the captured radiation may be an optical guide, preferably, an optical fiber, more preferably, a plurality of optical fibers.
An additional guide system may be added to the coating thickness monitor. This additional guide system is capable of transmitting at least a portion of the radiation from the at least one radiation source to direct at least a portion of the radiation at at least a portion of the anodized substrate. The additional guide system may be an additional optical guide, preferably an optical fiber, more preferably, a plurality of optical fibers.
Also, a supplementary guide system may be added to the coating thickness monitor. The supplementary guide system is capable of at least one of: (1) transmitting additional captured radiation from the at least one probe to the at least one detector; (2) transmitting at least a portion of the radiation from at least one additional radiation source to direct at least a portion of the additional radiation at at least a portion of the anodized substrate; and (3) transmitting at least a portion of the additional radiation from at least one additional radiation source to direct the at least a portion of the additional radiation at at least a portion of the anodized substrate and transmitting the additional captured radiation from the at least one probe to the at least one detector, the additional captured radiation being at least a portion of the additional radiation directed at the anodized substrate from the at least one additional radiation source. The supplementary guide may be an additional optical guide, preferably an optical fiber, more preferably a plurality of optical fibers.
The guide system and the supplementary guide system are selected to be capable of transmitting a broad spectral range of captured radiation from the at least one probe to the at least one detector.
In one embodiment, the at least one radiation source is polychromatic and includes at least one of ultraviolet radiation, visible radiation, and infrared radiation. In another embodiment, the at least one source radiation is monochromatic. An additional radiation source may also be included with the coating thickness monitor. In one embodiment, the additional radiation is polychromatic and includes at least one of ultraviolet radiation, visible radiation, and infrared radiation. In another embodiment, the additional radiation is monochromatic. In a preferred embodiment relating to at least one radiation source and an additional radiation source, a spectral range of the at least one radiation source and a spectral range of the additional radiation source partially overlap. The partial overlap increases at least one of a signal to noise ratio for the captured radiation and a total spectral range of captured radiation. Preferably, one of the at least one radiation source and the additional radiation source is visible radiation and the other of the at least radiation source and the additional radiation source is infrared radiation.
The at least one probe may further include a collimator that facilities a depth of field of a sufficient value to measure the anodized coating thickness. In one embodiment, the at least one probe is external to the bath. In an alternative embodiment, the at least one probe is within the bath.
The at least one detector may include an interferometer. The processing of the captured radiation to determine the coating thickness by the coating thickness monitor includes at least one of using a color, using an interference pattern, using an amount of absorbed radiation, using an intensities ratio of a minimum reflected radiation wavelength and a maximum reflected radiation wavelength, and using a Fast Fourier Transformation (FFT) of the captured radiation. Preferably, the processing of the captured radiation to determine the coating thickness by the coating thickness monitor includes using a Fast Fourier Transformation (FFT) of the captured radiation.
Accordingly, one aspect of the present invention is to provide an anodizing system for forming an anodized coating on at least a portion of a substrate thereby creating an anodized substrate. The anodizing system includes a bath and a coating thickness monitor. The substrate is placed into the bath to facilitate the formation of the anodized coating on at least a portion of the substrate thereby creating the anodized substrate. The coating thickness monitor measures the thickness of at least a portion of the anodized coating on the substrate formed in the bath. The coating thickness monitor includes at least one radiation source directed at at least a portion of the anodized substrate, at least one probe for capturing at least a portion of the radiation reflected and refracted by the anodized coating on the anodized substrate, the captured radiation being at least a portion of the radiation directed to the anodized substrate from the radiation source, and at least one detector in communication with the at least one probe, the at least one detector capable of processing the captured radiation to allow a determination of at least the thickness of the anodized coating on the substrate.
Another aspect of the present invention is to provide a coating thickness monitor for measuring the thickness of at least a portion of an anodized coating on at least a portion of a substrate. The anodizing system has a bath into which the substrate is placed to facilitate the formation of the anodized coating on the substrate thereby creating the anodized substrate. The coating thickness monitor includes at least one radiation source directed at at least a portion of the anodized substrate; at least one probe for capturing at least a portion of the radiation reflected and refracted by the anodized coating on the anodized substrate, the captured radiation being at least a portion of the radiation directed the anodized substrate from the radiation source; at least one detector in communication with the at least one probe, the at least one detector capable of processing the captured radiation to allow a determination of at least the thickness of the anodized coating on the substrate, and a guide system capable of transmitting the captured radiation from the at least one probe to the at least one detector.
Still another aspect of the present invention is to provide an anodizing system for forming an anodized coating on at least a portion of a substrate thereby creating an anodized substrate. The anodizing system includes a bath, a coating thickness monitor, at least one probe and at least one controller. The substrate is placed into the bath to facilitate the formation of the anodized coating on at least a portion of the substrate thereby creating the anodized substrate. The coating thickness monitor measures the thickness of at least a portion of the anodized coating formed on the substrate in the bath. The coating thickness monitor includes at least one radiation source directed at at least a portion of the anodized substrate, at least one probe for capturing at least a portion of the radiation reflected and refracted by the anodized coating on the anodized substrate, the captured radiation being at least a portion of the radiation directed the anodized substrate from the radiation source, at least one detector in communication with the at least one probe, the at least one detector capable of processing the captured radiation to allow a determination of at least the thickness of the anodized coating on the substrate, and at least one guide system capable of transmitting the captured radiation from the at least one probe to the at least one detector. The at least one controller is in communication with the coating thickness monitor and the bath.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiments, when considered with the drawings.